Optical system for photographic composing apparatus



March 1954 s. H. CALDWELL OPTICAL. SYSTEM FOR PHOTOGRAPHIC COMPOSING APPARATUS Filed March 10, 1950 Patented Mar. 2, 1954 [TED estates mares oasis-E "I OPTICAH SYSTEM FOR PHOTGGRAIP-HIC '-GOM-POSING APPARATUS Samuel Ho Caldwell, BostomlMass assignor-to GraphicvArts Research Fouhdatioii lncl;Cam- T .bridgaI'Mass a corporation of Delaware application March 10, I950, Serial Nox1148;901

Glaims :pr-iority, application .Erance JMarch 17,:1949

fitiiaims. 1 "iflhls'inventi'on "relates to, photographic com- 1 posing apparatusgand more particularly to apg'pa'ratus'" for .projecting. the selected, characters 1 upon a sensitized material.

1A. necessary function I of -such apparatus, is to v.cause, i relative .motion Jaetweenl.v the ,projected character images .and ..the.. sensitized surface. ""This motion usually depends upon the widthsllof the .ccharacterscand upon; thehincrements L-to be sanded between words and l.charactersto justify ilthelline. "IThis motion. must. also be. performed .lwithspeedandiprecisioncommensurate ivithithe .Zl desired..accuracyiin ithe alignment ofrcharacter aprojections.

inn-Hitherto; and for: cexampleaas; shown ;-;in '2 the i. r-calied tlinegspacing. '2 The vrequirenrient:ofi'speed',

::particularly:-;where: the;:.. motion: is :inter'mittent, i. .--places a -:premium .on' :lighttcohstruction; ihutxthis objective isxinaconflictrn'riith theztrequirementtof .aaccuracyf of"positioningziwhichopiaces aztpremium iron 'sturdy 'zconstruction.

c-Anrrobject oftthenpresentsinvention is'ito procvide apparatus: fortcharacter: spacing lwlrich recqnires onlyzthezmovement. of; lightweight, lowinertia; elements.

Az further object is: to provide-apparatus ior ::character spacingpwhich:is aclapted to any-=appropriate mechanical means for producing transa: ziatoryr motion -whether" or -*not the motion-'- is a niultiple of some unitary distance.

Y A" further objectis-to' provide"apparatus-for "-"'characterispacing" which" can 'bBTUSGCY either "to produce undistorted proj ected' images; or to: dis- "tort thexprojected images to produce'othershapes "ofiiiyp According to the present invention .the-iunctionfof characterspacin'g is performed lwithinthe opticalfsystem. itself, the respectivei elements f which areimade re1ati'vely movab1e. "'L'Thesupcportw'h'ich carries thefilmlmorvesonly for'the Durposeffofj line spacing? Theopticalrsystem is I designed, in amanner tohehereinafteridescrihed, itol'iitilize the properties Tofacollimating. lens.

TWith' theT'abovefob-ject'siin view, other. features of the invention comprise certain features of construction 'andmodes ofoperati-on hereinafter described"andparticularlydefinedin'the claims.

' In theaccom'panying'drawings Fig. 1 is a'sectional elevation "ofthe "apparatus Fig; 2 is an end elevation through section 2-2""0f Rig. 1,

" showing in'a'ddition a preferred formoffilmsupport'j Fig; 3 is adiagramniatic'representationof the relationship "between lenses 3' andj 4f;'"Fig. 4 is ascheniatic representation of aform'oftheizinvention empioying adrum'a'sithe character carrier; and Rig. 5 is a diagrammatic representation of means "for insuring uniform hrilliancebiproi ected images.

In Fig. 1' the matrix disc I: is rotatably mounted on a frame, shown inmpartat .13, ahdlcarrie'sithe characters to be projected isuccessively ,past. a

a stationary i character v aperture fl 5. TI'LTheR characters are disposfejdin a circle on thediscl "I'Ihfiash oriilluminating' device 2 isipreferablyiofithe type described inlthe copendingapplicationiof HighnnetiandMoyrohdserial1No.,.6l0;336,;fi1edAugust i 11,,"1945, .iwhe'reby alfiashaoccursiati the precise instant that the. selected character .onitheidisc is in position t'ohe projected, this positionebeingiin illuminating:device; is-vpreferablytcontroliedcby a eregister in i which alli'the. characters-oi alineiare rstoredbefore projection, and meansiareactuated Qby ithevregisteri toaselect v-thewsuccessiva stored .charactersfor: projection.

.rRigidly mountedron-framedfi is aeiensssupport l t-Whichmaysbesasfshown; :irr the. form oiz aahol- 10w tube with the character aperture l5 at-c-one it end. Mounted-in theiens support 1: is azcol'limating. .lens 3-01" iocaldength ,fi; thEzDOSitiOflOf which iswsuch' thatithe characters on,the :rotating- .-disc e arerin its focal: plane.

siidablysmounted in. the lens support is a-trans- -2 lating-.-1ens combinationicomprising a converging 4O :lons 450i; focal ;.:1ehgth: faiand azzright angleireing deviceysuch as a pentaprisnror a mirror' may bs usedlinplacehf thep-rism 5.--' A rod l6 isattached to sliding"-mount fi andicarries aqrack meshing with the teethbf apinionfl l,-'rotatab1y mounted" on the frame "I 3. The *pim'orr is provided with "means," shown" diagrammaticatlly .at

1 '28,; toicause rotation atldiscrete times by angles proportional to .the desiriedspacin'g.betweerrsuccessive projections.;;Means performingssuch a function are disclosed in the pending application of Higonnet and Moyroud, Serial No. 610,336, filed August 11, 1945. The variable advance mechanism there used is limited to movements which are multiples of a unitary movement. It will be clear, however, that the present invention is not limited to such means, and can be driven by steps of any desired size.

It is necessary that sensitized surface 8 falls in the plane of focus of lens 4. The exact determination of this position must take into account the passage of the converging rays through glass, as will be clear to those familiar with this art.

In Fig. 2, the sensitized surface 8 is shown in the form of a film wound over two spools B and I2. The spools are rotatably mounted on the frame I 3. The film 8 passes from spool 9, around idler wheels H and i4, through a channel in a guide l8, fixedly mounted on frame it and provided with an exposure slit to receive projected characters, around a toothed driving sprocket Ill, an idler wheel l9, and onto take-up spool 12. A cover, not shown, protects the film from exposure except through the slit in guide l8. Driving sprocket l0 may be actuated at suitable times to cause line-spacing.

The optical system above described must have certain properties which cause it to move the successive projections along the sensitized surface without distortion or change in size. That these properties may be obtained is made clear by an examination of Fig. 3. Lenses 3 and i, separated by a distance it, are shown on a common central axis b-b. The focal distances of the respective lenses are measured off on the line b-b' from their centers. to be projected is shown as an arrow in the focal plane of lens 3. When the character is illumi nated the rays emerging from any part thereof, say, for example, the tip of the arrow, will be pointed in all directions. upon two particular rays is immediately apparent. Ray 20, passing through the center of the lens, is not bent because it passes through two parallel surfaces. (For purposes of this description it is assumed that the lens is thin enough that the linear shift in the ray may be neglected.) Ray 2|, being parallel to central axis b-b', will be bent so that it will pass through the focus on the other side. By construction, it is seen that these two rays emerge from lens 3 parallel to each other. Similarly, all other rays emerging from the tip of the arrow and passing through lens 3 will be parallel to these rays.

Of all the rays emerging from the tip of the arrow and passing through lens 3 a number will also pass through lens 4, provided that lens 4 is not so far removed from lens 3 that none or the rays will impinge upon it. The effect of lens 4 upon two of these rays is immediately apparent. Ray 22, passing through the center of the lens, is not bent, since it passes through two parallel surfaces. Ray 23, passing through the focus of the lens, will emerge therefrom parallel to axis b-b. Rays 22 and 23 are seen by construction to converge upon a point in the focal plane of lens 4. Similarly, all other rays emerging from the tip of the arrow will focus at the same point if they pass through lens 4.

A ray emerging from the focal point of lens 3 and traveling along axis 21-12 will be bent by neither lens because it passes through parallel surfaces. Hence, it will pass through the focal point of lens 4. So also will all other rays emerging from the base of the arrow.

The character The effect of the lens It may be seen by construction that the image is inverted, and the resultant magnification of the image is equal to the ratio of the respective focal lengths. Also, the distance h has no effect upon the distance from lens 4 at which the image will focus. This distance and the magnification remain constant with variable h.

The introduction of prism 5 at a point within the focal length of lens 4 reflects the rays, which are at this point converging, to cause them to converge upon the sensitized surface 8.

From an examination of Fig. 3, it is evident that if the diameters of the lenses 3 and 4 are equal there will be a diminution in the brilliance of the character images as the lens 4 is moved away from the lens 3. This is caused by the fact that, although all of the rays emanating from a particular point in the object and passing through the lens 3 will be parallel to each other, they will not be horizontal. It is further evident that the angle which the parallel rays make with the horizontal increases with the distance of the point in the object from the optical axis. As the lens 4 moves away from the lens 3, it will collect an ever decreasing part of the pencil of rays emanating from a particular point in the object. The resulting effect is to vary the effective ex-- posure on the film from one end of the line to the other.

In Fig. 5, apparatus is shown whereby it is possible to eliminate the changes in brilliance of the images above mentioned. This is done by using a lens 3 of larger diameter than the lens 3, whereby the lens 4 receives substantially the complete bundle of rays from the collimating lens 3, regardless of the distance between lenses. Two positions of the lens 4 are shown, one at A in full lines, the other at 4' in dash lines. For the dimensions of the object and lenses shown, the substantial limit of the range of movement for uniformity of illumination is indicated at 4. In view of the latitude of the film and the fact that gradations of density in the photographic image are not required, some extension of the range is possible.

Since polychromatic light will usually be employed, it is desirable that the lenses be at least partially corrected for color, but simple achromats will usually suffice. In other respects, a high degree of correction is not required. l' his follows from the fact that each lens has either its image or object at or near infinity. The lenses may be of very large apertures. As is evident from Fig. 5, only a small part of the covering power of the converging lens is used, and the aberrations which are important in camera lenses are not of primary concern in the present invention.

It will be understood that the characters will be so disposed on the disc that the inversions effected by the lenses and the prism will produce images with correct orientation on the film, as will be clear to those familiar with this art.

Since the magnification of the system is equal to the ratio of the focal lengths, a simple method of changing the type size of the projections without changing the sizes of characters on the matrix disc is to replace either lens, making proper adjustments to take account of the new focal distances. In the form of the invention shown in Fig. l the simplest method is to replace lens 3.

If it is desired to produce a distortion of the projected characters the prism may be turned to cause the projections to impinge upon sensitized surface 8 at angles less than or greater than ninety degrees. This will take the resultant focal plane out of coincidence with the sensitized surface, and will cause it to intersect the surface in only one line. The result will be to produce shrinkage in a particular dimension relative to the dimension at right angles thereto. If the focal length f: is long enough, the edges of the projections will not become noticeably out-of-focus.

An alternative embodiment of the invention, as shown in Fig. 4, comprises a rotating character drum 50 mounted on a shaft Bands of characters 52, 53 and 5%, each band representing a different font, are placed around the drum. Flash lamps 55, 56 and 5'! are fixedly mounted in position to project the characters of a particular font. A lens 58, a collimating lens corresponding to lens 3 in Fig. 1, is fixedly mounted with a prism 59, the combination being movable along the axis of the lens mount to select the font to be projected. A prism 51, a lens 68 and a sensitized surface 53, correspond to prism 5, lens 4 and sensitized surface 8 in Fig. 1. The advantage of the arrangement resides in the ease with which the font may be changed due will employ lenses suitably corrected in accordance with well-known optical principles.

Having thus described the invention, I claim: 1. In photographic type composing apparatus,

the combination of a collimating lens, means for putting in the focal plane of the collimating lens an image of the character to be projected, an illuminating device to project the images of selected characters forming a line successively through the collimating lens, each character having a predetermined width value and being projected while it is in the projection position, a translating lens combination including a converging lens and a reflector arranged one behind the other to focus the projected light and reflect it through a predetermined angle, a support to hold a sensitized surface in substantial coincidence with the focal plane of the light leaving the lens combination, and means for displacing the lens combination relative to the collimating lens and longitudinally of the surface after each projection by variable distances proportional to the widths of the corresponding characters, whereby each character is focused upon the surface irrespective of the relative positions of the two lenses.

2. In photographic type composing apparatus, the combination of a collimating lens, a matrix disk revolving about a fixed axis bearing a plurality of characters arranged in a circle lying in the focal plane of the collimating lens and having its center in the said axis, whereby the characters are moved through a projection position, an illuminating device to project the images of selected characters forming a line successively through the collimating lens, each 6 character having a predetermined width value and being projected while it is in the projection position, a translating lens combination including a converging lens and a reflector arranged one behind the other to focus the projected light and reflect it through a predetermined angle, a support to hold a sensitized surface in substantial coincidence with the focal plane of the light leaving the lens combination, and means for displacing the lens combination relative to the collimating lens and longitudinally of the surface after each projection by variable distances proportional to the widths of the corresponding characters, whereby each character is focused upon the surface irrespective of the relative positions of the two lenses.

3. In photographic type composing apparatus, the combination of a drum revolving about a fixed axis, a number of circular bands of characters disposed upon and relatively displaced longitudinally of the drum, each band corresponding to a different font, a first optical system comprising a collimating lens and a first reflector in fixed relation, said optical system being movable in a line parallel to said axis to select the desired band, whereby the characters in the selected band pass successively through the focal plane of the collimating lens, an illuminating device to project the images of selected characters forming a line successively through the collimating lens, each character having a predetermined width value and being projected while it is in said focal plane, a second optical system comprising a converging lens and a second reflector arranged one behind the other to focus the projected light and reflect it through a predetermined angle, a support to hold a sensitized surface in substantial coincidence with the focal plane of the light leaving the second optical system, and means for displacing the second optical system relative to the first optical system and longitudinally of the surface after each projection by variable distances proportional to the widths of the corresponding characters, whereby each character is focused upon the surface irrespective of the relative positions of the two optical systems.

4. Apparatus as defined in claim 1 in which the converging lens is of larger diameter than the collimating lens, whereby the image is illuminated in a substantially uniform manner over the range of relative displacement of the lenses.

5. Apparatus as defined in claim'3 in which the converging lens is of larger diameter than the collimating lens, whereby the image is illuminated in a substantially uniform manner over the range of relative displacement of the lenses.

SAMUEL H. CALDWELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 198,240 Drummond Dec. 18, 1877 1,589,797 Eppenstein June 22, 1926 3,1 Chireix et a1. Jan. 3, 1933 2,132,089 Mihalyi Oct. 4, 1938 

